If you do decide to DIY, read this:
http://www.bikeforums.net/showthread...bikes-to-SS-FG
The CL link is dead, but 30 lbs. isn't unreasonable for a cheap 70's 10 speed. However, a 70's Varisty weighs close to 45 lbs. D8

Expect to drop around 4-5lbs. on a conversion: Vintage multispeed freewheels are heavy, and the lack of derailleurs, shifters, and cables doesn't hurt, either.